package algorithm.lanqiao.t19695;

import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;


public class Main {
    static InputStreamReader ins = new InputStreamReader(System.in);
    static StreamTokenizer in = new StreamTokenizer(ins);
    static PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));

    public static void main(String[] args) {
        int ans = 0;
        for (int i = 50; i > 7; i--) {
            ans += (i - 1);
        }
        out.println(ans);
        out.flush();
    }

    private static int readInt() {
        try {
            in.nextToken();
        } catch (Exception e) {
        }

        return (int) in.nval;
    }
}
